1. International Association of Scientific Innovation and Research (IASIR)
(An Association Unifying the Sciences, Engineering, and Applied Research)
International Journal of Emerging Technologies in Computational
and Applied Sciences (IJETCAS)
www.iasir.net
IJETCAS 14-476; © 2014, IJETCAS All Rights Reserved Page 508
ISSN (Print): 2279-0047
ISSN (Online): 2279-0055
Investigation of the Influence of Power Density and Frequency on Laser
Drilling in Metal Samples
Nikolay Angelov
Department of Physics, Chemistry and Ecology
Technical University of Gabrovo
4 Hadhy Dimitar str., Gabrovo, 5300, Bulgaria
Abstract: To study the influence of the main parameters on the process of laser drilling in various samples from
aluminium, copper and silver, numerical experiments are carried out with specialized software
TEMPERATURFEL3D, working in MATLAB. The results refer to the fiber laser and CuBr laser - modern laser,
whose applications in various technological processes are still being explored. The dependences of the depth of
the hole on the power density and the frequency are obtained. Тhe influence of power density is analyzed.
Operating range for the frequency for the considered process is determined.
Keywords: numerical experiments, software, laser dilling, fiber laser, CuBr laser.
I. Introduction
Lasers are widely used in many areas – not only in laser processing of materials, in processing of thin films and
microstructures, in measuring equipment, in urban engineering, in medicine, in the military industry, in
agriculture, in holography but also for transporting information and processing it optically, for obtaining plasma,
for laser emission spectral analysis, and for many other purposes in science and education. Laser technology is
used in the processing of materials with huge success. This includes technological processes in metals and alloys
[1]-[3] such as marking and engraving, cutting, welding, drilling, scribing. For lasers’ widespread use for
practical purposes contribute the specific properties of the laser radiation - high coherence monochromaticity,
high directionality, ability to achieve high energy density (and power density, respectively) in the treated area.
Laser sources emit radiation with wavelengths in a wide range of the spectrum - from ultraviolet , through visible
and to infrared in both continuous and pulsed modes. Furthermore, in recent years new lasers were constructed
with the appropriate characteristics and properties to provide the required technological parameters for treatment
of the materials.
II. Presentation
The purpose of the study is to investigate the influence of the power density and to determine of the operating
range for the frequency for drilling holes in samples of aluminum, copper and silver via fiber laser and CuBr
laser. A large number of numerical experiments are conducted with the software TEMPERATURFEL3D [4],
working in MATLAB. It provides the following options for the output results:
 Animation of the whole process;
 Temperature profile of the sample in a given time;
 profile of the maximum temperature;
 temperature’s dependence on time;
 temperature changes of the sample in the depth.
The realization process of laser drilling depends on the thermo-physical and optical properties of the material
[5]-[6]. This requires conducting experiments in the specific metals. Table I shows some basic characteristics of
the studied materials [7]-[8].
Table I. Some thermophysical paramerters of the metals aluminium, copper and silver
Metal
Magnitude
Aℓ Cu Ag
Thermal conductivity k, W/(m.K) 236 401 429
Specific heat capacity c, J/(kg.K) 830 380 232
Density ρ, kg/m3
2700 8920 10490
Diffusion coefficient a, m2
/s 1,05.10-4
1,18.10-4
1,76.10-4
Temperature of melting Tm, K 933,5 1357,6 1235
Temperature of evaporation Tv. K 2972 2830 2435
Numerical calculations have been made in two directions:

2. Nikolay Angelov, International Journal of Emerging Technologies in Computational and Applied Sciences, 8(6), March-May, 2014, pp508-
512
IJETCAS 14-476; © 2014, IJETCAS All Rights Reserved Page 509
 Investigation of the influence of power density.
 Determining the operating range for the frequency.
The main parameters of the lasers and the technological systems to which the numerical experiments are applied
are given in Table II [9]-[10].
Table III. Some basic parameters of the used lasers and technological systems
Laser
Parameter
Fiber laser CuBr laser
Wavelength λ, nm 1064 511
Power P, W 100 50
Frequency ν, kHz 50 20
Quality of beam M2
1,1 1,3
III. Results of numerical experiments
A. Investigation of the influence of power density
Large number of numerical experiments are conducted and analyzed. Through the computations the
power density is changed in the intervals qS Є [6,00.1010
; 8,25.1010
] W/m2
with a step of 0,25.1010
W/m2
for
fiber laser and qS Є [4,00.1010
; 6,25.1010
] W/m2
with a step of 0,25.1010
W/m2
for CuBr laser. The treatment
time is kept constant and the frequency is ν = 20 kHz for both of the lasers.
Fig. 1 and fig. 2 show the dependence of the depth of the hole h on the power density qS for the fiber
laser and the CuBr laser, respectively. From them, the following conclusions are reached:
Figure 1: Dependence of the depth of the hole h on the power density qS for the fiber laser for: 1)
Aℓ; 2) Ag; 3) Cu
100
120
140
160
180
200
220
240
260
280
5.5 6 6.5 7 7.5 8 8.5
h,m
q , 10 W/mS
10 2
μ
1
2
3
 As the power density increases a nonlinear increase in the depth of the hole for both lasers is observed;
 The speed of growth of the depth of the hole in the interval qS Є [6,50.1010
; 8,25.1010
] W/m2
for fiber
laser is:
- 3,83.10-9
μm/(W/m2
) in Aℓ;
- 3,54.10-9
μm/(W/m2
) in Ag;
- 3,26.10-9
μm/(W/m2
) in Cu.
 The speed of growth of the depth of the hole in the interval qS Є [4,50.1010
; 6,25.1010
] W/m2
for CuBr
laser is:

3. Nikolay Angelov, International Journal of Emerging Technologies in Computational and Applied Sciences, 8(6), March-May, 2014, pp508-
512
IJETCAS 14-476; © 2014, IJETCAS All Rights Reserved Page 510
- 4,63.10-9
μm/(W/m2
) in Aℓ;
- 4,23.10-9
μm/(W/m2
) in Ag;
- 3,83.10-9
μm/(W/m2
) in Cu.
Figure 2: Dependence of the depth of the hole h from the power density qS for the CuBr laser for:
1) Aℓ; 2) Ag; 3) Cu
70
90
110
130
150
170
190
210
230
250
3.5 4 4.5 5 5.5 6 6.5
h,m
q , 10 W/mS
10 2
μ
1
2
3
 In order to achieve a certain depth of the hole using a fiber laser 25% more power density is required
than that for the CuBr laser. This is caused by the different absorption rates of the laser radiation for the
two wavelengths.
B. Determining the operating range for the frequency
During the numerical experiments the frequency is changed in the interval ν Є [6, 20] kHz with a step of
2 kHz for the CuBr laser and ν Є [10, 50] kHz with a step of 5 kHz for the fiber laser. The influence time is kept
constant and the power density is qS1 = 7,50.1010
W/m2
for the fiber laser and qS2 = 5,25.1010
W/m2
for the CuBr
laser.
Figure 3. Dependence of the depth of the hole h on the frequency ν for the fiber laser for: 1) Aℓ; 2)
Ag; 3) Cu
180
190
200
210
220
230
240
250
260
270
0 5 10 15 20 25 30 35 40 45 50
h,m
v, kHz
μ
1
2
3

4. Nikolay Angelov, International Journal of Emerging Technologies in Computational and Applied Sciences, 8(6), March-May, 2014, pp508-
512
IJETCAS 14-476; © 2014, IJETCAS All Rights Reserved Page 511
Figure 4. Dependence of the depth of the hole h on the frequency ν for the CuBr laser for: 1) Aℓ; 2)
Ag; 3) Cu
120
130
140
150
160
170
180
190
200
210
220
0 2 4 6 8 10 12 14 16 18 20
h,m
v, kHz
μ
1
2
3
Fig. 3 and fig. 4 show the dependence of the depth of the hole h on the frequencies for the fiber laser and
the CuBr laser, respectively. From them, the following conclusions are reached:
 As the frequency increases a nonlinear increase in the depth of the hole in the intervals ν Є [10, 20]
kHz for the fiber laser and ν Є [6, 10] kHz for the CuBr laser is observed. In the intervals ν Є [20, 50]
kHz for the fiber laser and ν Є [10, 20] kHz for the CuBr laser there is a very slow linear increase in the
depth of hole;
 The speed of growth of the depth of the hole in the interval ν Є [20, 50] kHz for the fiber laser is:
- 0,40 μm/kHz in Aℓ;
- 0,35 μm/kHz in Ag;
- 0,30 μm/kHz in Cu.
 The speed of growth of the depth of the hole in the interval ν Є [10, 20] kHz for the CuBr laser is:
- 0,75 μm/kHz in Aℓ;
- 0.62 μm/kHz in Ag;
- 0,50 μm/kHz in Cu.
 The operating ranges for the frequency are:
- ν Є [20, 50] kHz for the fiber laser;
- ν Є [10, 20] kHz for the CuBr laser.
III. Conclusion
The obtaining of operating ranges for the frequency are required for the conducting real experiments and
the creating of technological tables with the optimal parameters for laser drilling. The latter are to assist the
operator of the technological laser system. Usage of technological tables leads to shorter time to deployment of
the technology in the production process, when the product’s material is changed.
IV. References
[1] Valiulin A, S. Gornii, Yu. Grechko, M. Patrov, K. Yudin, V. Yurkevich, Горный, Ю.Гречко, М.Патров, К.Юдин, В.Юревич Laser
Marking Materials, Scientific and Technical Journal PHOTONICA, Issue № 3/2007
[2] Grigoryanc A., I. Shoganov, A. Misyurov, Technological Processes of laser processing, MGTU “N. Bauman”, Moscow, 2006
[3] Schuőcker D. Handbook of the Eurolaser Academy, CHAPMAN&HALL, London, 1998
[4] Belev I., Environment for computation of laser-induced temperature fields, Master Thesis (Bachelor), Technical University of
Gabrovo, 2009

5. Nikolay Angelov, International Journal of Emerging Technologies in Computational and Applied Sciences, 8(6), March-May, 2014, pp508-
512
IJETCAS 14-476; © 2014, IJETCAS All Rights Reserved Page 512
[5] Garnov S., V. Konov, O. Tsarkova, F. Dausinger, A. Raiber High-temperature measurements of reflectivity and heat capacity of metals
and dielectrics at 1064 nm, Laser-Induced Damage in Optical Materials, 1996
[6] Angelov N., Process optimization marking with laser radiation on samples of tool steel, Dissertation for Acquiring Scientific and
Education Degree "PhD", Technical University of Gabrovo, 2011
[7] www.acsys.de
[8] www.pulslight.com
[9] http://www.ptable.com/?lang=bg
[10] http://www.splav.kharkov.com/choose_type.php